Traffic control system



Nov. 30, 1937. J. LQBARKER 2,100,831

TRAFFIC CONTROL SYSTEM Filed Fb. 4, 1937 3 Sheets-Sheet 1 Pap 0= A *5mmvrox Jaw L 542K512 ATTORNEY Nov. 30, 1937.

J. L. BARKER TRAFFIC CONTROL SYSTEM Filed Feb. 4, 1957 5 Sheets-Sheet 2'INVENTOR. 9 Jam L D4RKE BY vl.....rmfa.....

' A TTURNEY Nov. 30, 1937. Q E 2,100,831

TRAFFIC CONTROL SYSTEM Filed Feb. 4, 1957 3 Sheets-Sheet 5 AM CoumcrAlt/M5525 INVENTORI JOHN L. BAR/ff? BY ATTORNEY Patented Nov. 30, 1937UNITED STATES PATENT OFFICE TRAFFIC CONTROL SYSTEM John L. Barker, WhitePlains; N. Y., aaslgnor to Automatic Signal Corporation, East Norwnlk,Com, a corporation of Delaware Application February 4, 1931, Serial No.124.011

' 14 Claims. (01. 111-431) The invention disclosed herein relates totrafflc control apparatus and more particularly to apparatus of thetraiiic actuated type and has for its general purpose the provision ofan ap.

paratus adapted to control with a maximum of expediency and withoutconflict the flow of traific thru an intersection where several trafliclanes meet or cross.

This system is of the traiilc controlled typ and the particularembodiment shown in the accompanying drawings is adapted to be used atthe intersection of four trafllc lanes, three applied herein to aspeciflc type of intersection, is

not restricted thereby to any one type of intersection.

It is an object of this invention to provide an improved form of traflicactuated apparatus by means of which tramc will be expeditiously andautomatically handled so that a maximum trafflcflow thru the commonintersection of more than two lanes may occur without danger ofconflict.

It is an object of this invention to provide trailic actuated apparatusof an improved type adapted to control, with a maximum of emclency andsafety, the traillc at an intersection where a stop signal in otherlanes from which trafllc --would conflict with that entering theintersection from the lane or lanes wherein the' said go signal is beingdisplayed.

It is a further object to provide an improved form of traihc actuatedcontrol of the nature described and adapted to accord right of wayperiods successively to the several lanes in a predetermined order inresponse to traiiic and adapted to omit the right of way period in alane wherein there is no traflic.

It is another object of this invention to'provide an improved form ofapparatus of the nature described wherein the duration of each period cmby the apparatuscan be individually and independently preadiustedwithout changing the duration of any other time period.

It is also an object of this invention to provide an improved form oftraflic actuated control apparatus for use at intersections where morethan two lanes meet and which has a go signal period for each lanedivided into an initial fixed period followed by a period variablebetween minimum and maximum limits by trafllc and which has a warningsignal period prior to each transfer of the go signal from one lane toanother with separate independent adjustment of the duration of all ofthese periods for each lane.

It is a further object to provide an improved form of traffic actuatedcontrol apparatus for use at an intersection where more than two lanesmeet adapted to accord the right of way to the lanes in a predeterminedorder in response to traillc and including a mechanism for determiningat the beginning of the warning signal period whether the right of wayhas beencalled to the lane next in said normal predetermined order or tothe lane next beyond such lane in said order, and if the right of wayhas not been called to the first named lane and has been called to thesecond'named lane to cause the right of way to be transferred to thesecond named lane instead of It is another object of this invention toprovide an apparatus of the type described in which during the whole ofthe warning signal display period in the lane from which the right ofway is being transferred another warning signal is displayed in the laneor lanes to which the right of way is next to be accorded whether thelast named lane is the next in the normal predetermined order of rightof way transfer or the lane beyond.

It is another object toprovide a trafllc actuated control apparatus ofthe type described in which is included a switching mechanism adaptedfor cyclic operation to normally accord the right of way to the lanes ina predetermined order in response to trafilc, such switching mechanismnormally assuming at suitably timed intervals successive positions ineach of which a different si vide a traflic actuated'control of thenature described including a mechanism which will operate at thebeginning of the warning signal period-if the. right of way period is tobe omitted in the lane to which it would normally next be accorded, suchmechanism being adapted to remain operated and to maintain the signaldisplay period at which time it will become deenergized and permit theright of way to be accorded to the lane beyond and further adapted toprevent approaching traffic in the lane in which the right of way periodis being omitted from interrupting such transfer but adapted to causethe right of way to be given at the next normal opportunity to suchapproaching traflic in the lane in which the right of way period isbeing omitted.

It is a further object to provide a traiiic actuated apparatus of thedescribed type in which the right of way is accorded to the lanes by asix position cyclic switching mechanism adapted to move into the sixpositions successively at suitably timed intervals but having apparatusas sociated therewith to time an additional period in three of the sixpositions thus making available in each of these three positions twosuccessive time intervals during which parts of the apparatus can becaused to perform different functions thereby causing the six-positioncyclic switching mechanism to operate so as to give in effect a cycle ofnine positions.

One embodiment of the invention will now be described with reference tothe accompanying drawings, in which:

Figure 1 is a plan view of an intersection equipped with this apparatusshowing the location of the traific signals, traffic detectors, and

the control mechanism. The several traflic flows or phases aredesignated by the letters A, B,

C and D.

Figures 2 and 3 jointly constitute a schematic circuit diagram of thecontrol apparatus including connections with the traflic detectors andthe traffic signals. The particular signal connections shown in Figure 3are arranged to provide a cautionary signal before the go signal as wellas after the go signal in each lane,

Figure 4 shows an alternative arrangement of the signal relays toprovide a cautionary signal in each lane only after the go signal hasbeen displayed therein.

The apparatus of this system accords the right of way to the variouslanes in conformity with the requirements of traflic as indicated thruthe actuations of traffic detectors located in the sev- 'eral lanes. Iftraflic is present in all lanes the right of way is accorded to them ina predetermined order and for a time period in each lane determined bytraflic. If there is no traflic on a particular lane the apparatus willomit the right of wayperiod on that lane and, without delay, accord theright of way to the next lane in the predetermined order in which tramcis present;

The apparatus is adapted to be adjusted so that in the absence oftraflic-the right of way will normally revert from lane to lane in apredetermined order at predetermined intervals or, by a differentadjustment, the right of way can be caused to normally revert to aparticular lane in the absence of traific in the other lanes, or,bystill another adjustment the right of way can be caused to remain onthe lane to which it was last called until called by trafiic to someother lane.

The go signal or rightof way period in. each lane is divided into twoparts, the first of which unchanged until the end of such warning signalis called the initial interval and is predetermined in time and is notaffected by traffic actuations. The second portion of the go signalperiod can be extended by traflic actuations occurring during this partof the go period in the lane in which the go signal is being displayed.If traflic is continuous in'the lane in which the-go signal is beingdisplayed and would therefore unduly extend the go signal periodthereon, a cross lane call, due either to waiting traffic or toadjustment of the apparatus to normally'revert to that lane,

will cause this go signal period to be limited to a predeterminedmaximum.

This apparatus is also adapted to automatical ly causethe right of wayto return to any lane at the first reasonable opportunity if, when saidright of way last left this lane a detector located therein had beenactuated within a predetermined time.

This apparatus is preferably arranged to cause a warning signal to bedisplayed for a predetermined periodto traffic in the lane or lanes fromwhich the right of way is about to be withdrawn and if. desired anotherwarning signal to be simultaneously displayed in the lane to which theright of way is next to be granted in order to notify traffic thereinthat it is about to receive the go signal;

The control apparatus of which the circuit diagram is shown in Figs. 2and 3, is of the type in which cams, fixed on a shaft which is revolvedin steps by a solenoid with a ratchet and pawl mechanism or othersuitable means, operate contacts to control relays which in turn controlthe signal indications. Other contacts, operated by cams on this shaftcooperate with relay contacts to connect the various timer circuitsproperly for the particular part of the signal cycle prevailing. Y

The timing of all periods is accomplished thru gas discharge tubes usedin-conjunction with 4 When the voltage on the condenser reaches thebreakdown voltage of the tube to which it is con- 'nected the tubebecomes conducting and causesthe condenser to discharge thru a relay theoperation of which terminates the period being timed and initiatesaction of the solenoid. In this embodiment of the apparatus all the timeperiods are independently adjustable so that different. periods applyingto the same lane or corresponding periods applying to diiferent lanescan be individually timed.

' Traffic actuated apparatus for controlling traffic at intersectionswhere more than two traffic lanes cross has been in use for some time.One such apparatus is described in the British Patent The apparatus ofthe above British patent is arranged to show a warning signal in a lanewhen the right of way is to be withdrawn thereirom but itdoes not show awarning signal immediately prior to the display of the go signal in thelane to which the right of way is next to be accorded.

Furthermore in the above apparatus correspending time periods indifferent lanes must be of .the same magnitude since no provision ismade for individual adjustments of these periods for each lane.

The embodiment of the invention shown in this application is anadaptation of the cam shaft type of traffic actuated control requiringno electric motor and employing gas discharge tubes with platecondensers wherein the variation of I the charge at a suitable rate is/instrumental in timing the several time periods. This type of controlhas proved eminently satisfactory and economical in'controlling traflicat intersections I selecting the lane to which the right of way is tobetransferred and, this mechanism operates in such a way as to accord theright of way only to those lanes to which it has been called either bytraffic actuation or by adjustment for normally reverting thereto in theabsence of traffic. In addition it has an improved form of rapidstepping mechanism which, during the warning signal display period,causes the cam shaft without signal changes to move rapidly thruintervening positions to the proper position preparatory to displayingthe go signal in the lane selected by the selecting mechanism mentionedabove.

Furthermore, the apparatus includes an improved mechanism adapted todisplay the warning signal concurrently in the lane from which the rightof way is being withdrawn and in the lane to which the right of way isnext to be accorded during the whole of a 'normal warning signal displayperiod in the first mentioned lane. This feature makes the green, amber,red, amber, green signal sequence in each lane available for use at anintersection where more than two traffic flows cross.

However, the apparatus disclosed herein is not limitedto the abovementioned signal sequence but can by a slight circuit change be adaptedto provide any one of several other signal sequences. Its adaptation toprovide a green, amber, red, red, green signal sequence in each lane isshown in Fig. 4.

The signals for controlling trafli'c in phase are connected in Figs. 3and 4 to the phase C signals in such a way as to permit phase D tratllcto move with both phase A and phase B.

By connecting the phase D signals in the same manner to the phase Asignals instead of the phase C signals, phase D trafflc can be given theright of way; simultaneously with phases B and C instead of with phasesA and B.

Or, by connectingihe traiiic phase...D signal similarly to phase Bsignals, phase D traflic will be given the right of way concurrentlywith phases C and A.

In the particular type of intersection shown in Fig. i trafllc flow Dconflicts with flow C only.

Therefore, the flow D signals are connected in Figs. 3 and 4 tothe'signals of phase C in order to give the trailic flow D the right ofway whileit is accorded to flow Aor flow B.

The embodiment of the invention depicted in Figs. 1, 2 and 3, which, asmentioned, is adapted to provide the signal sequence green, amber, red,

amber, green in each lane will first be described.

Referring to the details of Fig. 1, the lane from which traflic flow Amoves is designated as phase A", the lane from which trafllc flow Bmoves is designated as phase B", those from which traffic flow C movesare designated "phase C, and the lanefrom whichv D moves is designated"phase D.

In Fig. 1 the signal Sig. contains suitable green, yellow, and redlamps, lenses and/or reflectors or their equivalents for properlydisplaying indications of right of way, change of right of way andinterruption of right of way respectively to each of the several traflicphases. The

control apparatus labelled Control Box is lo-- cated at the lower leftcorner of the figure and the traflic detectors M, N and P are shown inphases A, B and C respectively. Connecting wires are indicated betweenthe signals, control box and the detectors.

It will be noted that no traflic detector is located in the phase Dlane. Traflicfiow D therefore has no means for calling or holding theright of way, such means being unnecessary since right of way isautomatically accorded to phase D whenever it is accorded to phase A orB.

With reference to the traffic flows indicated in Fig. 1 it can be seenthat the portion of phase B traffic which moves straight ahead crossesthe path of phase A traflic and would cause interference if both flowsmoved simultaneously. It is also evident that tramc moving straightahead out of phase C would cross both flow A and flow B. Hence trafllcflows A, B and C are mutually interfering.

The traific flowing straight ahead out of phase D on the other hand doesnot conflict with that flowing as indicated out of phase B and canobviously merge with that flowing out of phase A. However, the phase Dtraffic crosses phase C traflic. Thus it can be seen that phase Dtraific interferes with phase C trafic but not with that from phases-Aor B. It is for this reason that phase D tramc can be allowed to flow.simultaneously with that from phase A or phase B, but must be stoppedwhen phase C is given the right of way.

A complete signal cycle during which right of way is accordedsuccessively to the mutually interfering traiilc flows'A, B, and C,together with suitable warning or change signals displayed after eachaccord of right of way, requires six positions of the camshaft. In thepresent embodiment of the apparatus the camshaft is advanced from oneposition to the next by action of a solenoid. These movements of thecamshaft may each be of 60 degrees so that one revolution of thecamshaft corresponds to one complete signal/cycle, or the camshaft maybe arranged to provide a number of cycles of the signals during onerevolution in which case the camshaft is provided with for example, 12or 18 positions and each movement of,.,the camshaft up the solenoid isthru a correspondingly smaller angle.

- With the signals connected as shown in Fig. 3 the signals displayedin' the several rest positions of the cam shaft are as follows:

When the cam shaft is in position 1 the go signal is normally displayedto traiiic ,fiows A and D and when the cam shaft is in position 2 thewarning signal is normally displayed to trafflc flow A and to thetraific flow which is next to be accorded the right of way.

When the cam shaft is in position 3 the go signal is normally displayedto trafllc flows B and shaft position 6 a warning signal is normallydisplayed to traflic flow C and to the traflic flowswhich are next to beaccorded the right of way one of which is invariably flow D. 5 From theabove it can be seen that the go signal is shown to tramc flow D at alltimes except while the go signal or the warning signal is beingdisplayed to traiflc flow C.

There are two cases of transfer of right of way from a. phase.

C'ase 1.If, while the right of way is'accorded to one phase, eithertrafllc or adjustment of the equipment for normal reversion calls forthe right of way on the phase next in the normal order of progression,the right of way will be transferred thereto at the first break ofpredetermined time duration in the moving traiiic, or, if no such breakoccurs, at the end of the predetermined maximum period.

Case 2.If on the other hand, while the right of way is accorded to onephase, the right of way is called to a phase not normally next in theorder of progression, and thereis no call for the right of way on theintervening phase, the right of way will be transferred next to thecalling phase, said transfer taking place at the first break ofpredetermined time duration in the moving trafilc, or if no such breakoccurs at the end of the predetermined maximum period. 3 Under the aboveconditions, when the go signal is extinguished and the warning signal isdisplayed in the phase from which the right of way isbeing yielded, thestop signal is extinguished I and a warning signal is displayed to thephase to which the right of way is next tobe accorded, in the first caseto the phase next in the normal order of progression; and in the secondcase to the phase beyond -.that next in the normal order of progression.

If the right of way is to be transferred to the phase not next in thenormal order of progression, the above named warning signals will remaincontinuously displayed while the cam shaft is stepped rapidly thruintervening positions until it comes to rest in the position immediatelypreceding that in which the go signal is displayed to the phase to whichright of way is next to be accorded. During this cam shaft movement nosignal changes occur in any phase.

The cam shaft will then remain in the above mentioned rest position fora normal warning signal period during which time the .warning signalsremain displayed as described. I

At the end of the mentioned warning signal period the cam shaft will beadvanced one more position by action of the warning signal period timerwhich will be described later, and the transfer of the right of way willbe completed without any change of signal having occurred in the.intervening phase wherein the stop signal was continually displayed.

If a trafllc actuation occurs in the intervening phase while the rightof way is being transferredas described above, such actuation will notinterv fere with the transfer described but will be effective to callthe right of way to the intervening phase at the next opportunity.

The controller shown in Figs. 2 and 3 includes three timers. One,consisting of relay AS, tube FA and condenser QA, times'the initialinterval of the go signal period in each phase A diiferent chargingresistance for condenser QA in each phase permits the initial intervalsto be of different lengths in the difierent phases. 75 Another timer,consisting of relay CS, tube F I period of this timer is alsoindependently adjustable in each interval which it times. When timingthe vehicle interval portion of the go signal period this timer issubject to reset by trafiic actuations in the lane wherein the go signalis bein displayed.

A third timer, called the maximum timer, consisting of relay BS, tube FEand condenser QB, times a maximum period beyond. which moving traffic inthe go signal phase cannot hold the right of way against a call inanother phase. The maximum period for each phase is independentlyadjustable. This timer is also provided with a special low resistancecondenser charging circuit which is used to move the cam shaft rapidlythru the intervening positions when a phase is to be skipped under thecircumstances previously described.

The maximum timer is so arranged that whenever the right of way has beencalled to any phase it will operate during all subsequent intervalsuntil the right of way has been accorded to the phase to which it hasbeen so called. This timer will therefore be effective to move the camshaft into its next position at the end of a predetermined period, suchperiod being long enough so that the maximum timer will not operate todo this until the period of the timer normally timing 'each suchinterval has expired, and the said timer normally timing such intervalhas therefore obviously failed to function in its usual manner.

Relays AD, BD and CD are responsive to actuations of the traihcdetectors III, II, and I2, located in the A, B and C phase lanesrespectively. Each of these relays is-effective to call the right of wayto the phase with which it is. associated when the detector in thisphase is actuated during the warning or stop signal display periodtherein and each is effective to cooperate with the vehicle intervaltimer to prolong the go signal display period in the phase with which itis associated when operated by trafflc during the vehicle intervalportion of the said go signal display period.

Switch l3 when closed causes relay AD to operate and lock-in over aholding circuit so as to call the right of way to phase A but theholding circuit for'relay AD is opened at another point during thevehicle interval portion of the phase A go signal period so that theenergization oi relay AD to extend the phase A go signal display periodcan be occasioned only by trailic actuations of the A phase detector asexplained above. Switches l4 and I5 cooperate similarly with relays BDand CD respectively.

If all three of these switches are open the right of way will remain onthe phase to which it was last called until a traflic actuation occursin another phase. With only one of these switches closed'the right ofway will in the absence of traffic normally revert to the phase withwhich under the reverting system will remain on each phase to which itis accorded for a minimum time period extendable to a maximum timeperiod by trafllc actuations.

If the go signal display period on phase A is terminated by operation ofthe maximum timer instead of by operation of the vehicleinterval timer,so that the last vehicle which 'actuated the detector in phase A did nothave a full vehicle interval in which to pass thru the intersection, acall for the return of right of way is automatically set up thru theoperation of relay AD by the maximum timer when the latter operates.

Relays BD and CD are similarly operated to put in an automatic right ofway return call to their respective phases if the right of way period isterminated therein thru the operation of the maximum timer.

Ii. the right of way is called to a phase other than that normally nextin the order of progression, as has been explained, the cam shaft isstepped rapidlyandwithout signal display change thru thepositionswherein the preliminary warning signal andthe go signal wouldnormally bedisplayed to the omitted phase. This eifect is accomplishedin accordance with the invention by the operation of relay J which isarranged so that when a phase is to be omitted, this relay will beoperated at the beginning of the warning signal period of the precedingphase and will be thereupon eifective to energize the previouslymentioned rapid stepping timing circuit associated with the maximumtimer which will carry the cam shaft quickly thru the interveningpositions to its proper destination. In addition to the above, relay Jcooperates in selecting the phase to which the right of way 'is next tobe accorded and causing a warning signal to be displayed thereinsimultaneously with that displayed in the phase from which the right ofway is being withdrawn. The method by which this is accomplished willlater be explained in detail.

The initial interval and the vehicle interval period of the go signaldisplay period of each phase are timed in one camshaft position, therebeing one such cam shaft position for each of the three mutuallyinterfering phases. For example, both of the above mentioned portions ofthe phase A go signal period are timed while the cam shaft remains inposition 1, those for phase B are timed while the cam shaft is inposition 3 and those for phase C are timed while the cam shaft is inposition 5.

At the end of each initial interval relay AS of the initial intervaltimer, operates and deenergizes relay IV. -The deenergization of relayIV causes circuit changes which terminate the initial interval andinstitute the succeeding vehicle interval period of the go signal periodwithout changing the cam shaft position or signal dis- :play, all ofwhich will be explained later in detail.

' Relays AG, BG, CG, AY, BY, CY, AYX, BYX,

and CYX are effective to control the signal display in the severalphases and to properly connect some of the timing circuits therefor-aswill be explained later in the detailed description of the operation ofthe system thru a complete cycle of signal changes.

With trafllc waiting on each phase the right of way, as previouslymentioned, will be accorded to the three mutually interfering phases inthe order, A, B, and C.v Phase D, as before mentioned. is given theright of way except when it is accorded to phase C.

As the right of way is withdrawn from a phase there are, as previouslyexplained, two possibilities. Either it will be accorded to the phasenext in the normal order of progression or, if there is no rightof .waycall thereon, it will skip this phase and be accorded to the one beyond.The condition of relay J indicates to which of these phases the right ofway has been called and so determines which of these phases is to beaccorded the right of way.

If there is a call for. the right of way on the phase next in the normalorder of progression, relay J will be in deenergized condition and the15 sequence of operations will be such that the right of way will beaccorded to such next phase. If, on the other hand, there is no suchcall for the right of way to the phase next in the normal o;der ofprogression and there is a call for the right of way to be accorded tothe phase beyond, relay J will be energized at the beginning of thewarning signal period of the phase from which the right 01' way is beingwithdrawn. This operation of relay J will cause a different sequence ofoperations to occur and cause the right of way to be accorded to thephase beyond the one'next in the normal order of progression.

In general, it can be said that relay J cooperates to accomplish theseresults as follows: Considering first the energizing circuit for relay Jit can be seen that positive A. C. power is permanently supplied thruwire I6. Negative A. C.

1 power on the other hand can be supplied thru three different circuitsone of which will be completed during each warning signal period, if,and only if, the next phase in the normal order of progression is to beomitted.

Consider the particular circuit thru which relay J can be energizedduring the A phase warning signal period. This circuit starts atnegative A. C. power and includes wire I1, back contact bdii of relayBD, wire it, contact c1}! of relay AY, wire iii, the coil of relay J andwire l6 which connects with positive A. C. power. Relay AY is alwaysoperated during the phase A warning signal period and only during thisperiod. Therefore contact aqyi will be closed during each phase Awarning signal period.

If the right of way is to be accorded to phase B relay BD will have beenoperated and contact b116, of the above circuit, will consequently beopen. Both of the other two circuits supplying negative power to relay Jare open in the A phase w warning signal period and since the abovedescribed circuit is open at contact 'bdfl, it follows that when theright of way is leaving the A phase and going to the B phase, relay Jwill be deenergized. This fact, as will later be explained in detail,will cause the B phase warning signal to be energized with the A phasewarning signal during the A phase warning signal period. Y

If the right of way had not been called to phase B relay BD would not beoperated and contact b'd' oi" the above described relay J energizingcircuit would be closed. Hence when at the beginning of the phase Awarning signal period contact 0115 of relay AY is closed as previouslymentioned, the described energizing circuit for relay J will becompleted and relay J will operate.-

As soon as relay J does so operate the closure of contact 1 will providea by-pass around contact bdB which will hold relay J energized duringthe phase A warning signal period even though a phase B traflicactuation should operate relay BD and so open contact MB. This preventsa phase B actuation, occurring during the transfer of'the right of wayfrom phase A to phase C, from interrupting said transfer after it isstarted.

With relay J operated the phase C and phase D warning signals instead ofthe phase B warning signal will be energized with the phase A Warningsignal during the phase A warning signal period. This will later beexplained in detail. In addition to the above, the operation of relay Jduring the phase A warning signal period causes the special rapid timingcircuit of the maximum timer to function to step the cam shaft rapidlythru phase B positions which will also later be explained in detail.

The circuit by which relay J can be energized during the phase A warningsignal period has been described here in some detail. The other twomentioned similar circuits are effective under corresponding similarconditions to energize relay J during the phase For the phase C warningsignal periods wherein its functions are of the same nature as thosedescribed above in connection with the phase A warning signal period.

Operation of thisembodiment of the invention in transferring the rightof way thru a cycle from phase A to phase B then to phase C and thenback to phase A will now be described. It

will be remembered that phase D traflic is automatic'ally accorded theright of way with phases A and-B but not with phase 0. Phase D trafflchas no means for calling or holding the right of Way and is thereforenot a factor in controlling the transfer of the right of way. Hence itdoes not need to be considered in that respect.

The sequence of transfers given above omits no phase. Hence relay J willremain unoperated during the whole procedure. This being the case, itwill be remembered that in this part of the description involving nophase omissions all make contacts of relay J will be continuously openand all back contacts will be continuously closed.

The condition of the cam shaft contacts in each position of the camshaft is indicated in the table at the bottom of Fig. 3. In this tablean X in a square indicates that the cam contact whose number appears atthe top. of the column is closed when the cam shaft is in the positionidentified by the number at the end of the row in -which the 'X occurs.

Assume that the right of way has just been accorded to the phase A'andthat traffic is moving thereon, while traflic waits on phases B and C.The cam shaft is in position 1. Relays AD. BD and CD will each have beenenergized by traific'actuation of the detectors in their respectivephases. Relay BD energized by the circuit thru switch ll, relay BD andlead It will continue to be energized by a holding circuit thru therelayand over armature bdl and cam contact Cl8; relay CD will remainenergized by a similar holding circuit over armature cdl and cam contactCl3. Relay AD will remain energized over armature adl, lead 46, armatureivl3, and lead 45.

The go signal is displayed to trafflc on phases A and D whereas the stopsignal is displayed to B and 0 phase traflic. The A phase go signal AGSis energized thru a circuit starting at posi tive AC. power thence mmwire 20 to armature ayzrl and contact awe! of relay AYX, wire 2| toarmature cal and contact mp2 of relay AG to A cuit which accomplishesthis starts at D. C. plus phase go signal AGS thence to negative A. C.power.

Relay AG, which must be operated to complete the circuit describedabove, is energized in cam shaft positions 1 and 2 thru a circuit fromnegative A. C. power to contact 7'9 of relay J, wire 22 to cam contactC1 to the coil of relay AG thence to positive A. C. power.

The B phase stop signal BBB is energized from positive A. C. powerv thruwire 20 to armature byxl and contact byx3 of relay BYX, wire 23toarmature bgl and contact 1793 of relay BG, to the B phase stop signalBRS thence to A. C. negative power. v

The C phase stop signal CBS is energized thru a circuit from A. C.positive power thru wire 20 to armature curl and contact 01113 of relayCYX, -wire 24 to armature cgl and contact 093 of relay CG, to the phaseC stop signal CRS, thence to negative 'A. C. power.

In Figure 3 the D phase go signal DGS, which is displayed except when 0phase has the right of way, is energized thru the same circuit as the Cphase stop signal, and the D phase stop signal DRS is energized by thesame circuit as the 0 phase go signal.

As mentioned before, two successive periodsare timed in cam shaftposition 1, the first being the A phase initial interval. The initialinterval timer includes tube .FA, plate condenser QA and relay AS. Whilethe cam shaft solenoid S was in its operated position preparatory tomoving the cam shaft from position 6 'to 1, solenoid contact sl wasclosed thereby discharging'condenser QA thru the circuit from negativeD. C. power thru wire 25 to contact sl, resistance RA, wire 26 tocondenser QA thence thru wire 21 back tonegative D. C. power. Therefore,when the cam shaft reaches position 1 there is substantially no chargein condenser QA.

The timing of the phase A initial interval is accomplished thru chargingcondenser QA from substantially zero voltage up to the break-downvoltage of tube FA at a rate determined by the 'magnitude of resistanceAI. The charging cirpower thence thru variable resistance AI to contacti125 and armature jolt] of relay IV, contact C2, wire 26 to condenser QAthence thru wire 21 to D. C. negative power. The timing of the A 5 phaseinitial interval is adjustable by changing the value of variableresistance AI.

The charging circuit just described included contact 1'05 and armatureivlfl of relay IV, hence, a discussion of the energizing circuit forrelay IV is included at this point.

Relay'IV is energized as the solenoid is energized preparatory toremoving the cam shaft into positionsz, 4 and 6 thru the circuit from A.0. plus power to the coil of relay IV, wire 28 to contact s3 paralleledby contact C2l, and thence to A. C. negative power. This operatingcircuit is rendered incompleteby the opening of contact C2! and solenoidcontact s3 in cam shaft positions 1, 3 and 5, contact s3 being closedonly while the solenoid is energized. However relay IV has a holdingcircuit from positive A. C. power thru the coil of relay IV, contactiv'lof relay IV. wire 29 to back contact asl of relay AS and thence to A.'C. negative power. v

Relay IV, after each energization as described above, will be keptenergized by thisholding circuit until the end of the next subsequentinitial interval at which time, its above described operating circuitbeing open at contacts 83 and CZI, it will be released thru the openingof its holding circuit at contact as3 of relay AS, the initial intervaltimer relay. Thus it can be seen that the operating circuit and theholding circuit of relay IV cooperate to keep this relay energized atall times except during the vehicle interval of. each go signal periodduring which period the initial interval timer is being charged at apredetermined rate to time this period. When the voltage of condenser QAreaches the breakdown voltage of tube FA this tube will becomeconducting and condenser QA will thereupon discharge thru the coil ofrelay AS which relay will then operate.

The discharge circuit for condenser QA thru relay AS starts at negativeD. C. power thence thru condenser QA, wires 26 and 39 to tube FA,armature ivlG and contact i122 of relay IV, to contact C3l, wire 3| tocoil of relay AS thence back to negative D. C. power. The operation ofrelay AS does not cause the cam shaft to be moved but as previouslypointed out it does deenergize relay IV by opening its holding circuitat contact (:33.

The closure of contact asl of relay AS completes an auxiliary dischargecircuit for condenser QA thru coil of relay AS and resistance RA. Thecompletion of this direct discharge circuit insures that, although itspreviously described normal energizing circuit is opened upon thedeenergization of relay IV, relay AS will remain operated until thevoltage of condenser QA has been decreased to less than that required tohold relay AS operated.

The operation of relay AS also opens contact as2 in the relay CS coilcircuit and keeps this circuit open until relay AS assumes itsunoperated condition, i. e., until the voltage of condenser QA has beenlowered to such a degree that it would be ineffective to operate relayCS if connected to The above arrangement assures that when relay AS isenergized with the consequent deenergiza-v tion of relay IV, the energyremaining in condens er QA at that-time will not be passed thru relayCS. This prevents theopera'tion of relay CS at the end of the initialinterval of the go signal period;v When the energy in condenser QA hasbeen drained to a low level, relay AS will be deenergized and itstemporary auxiliary circuit will be opened at contact as! and the normalcircuit thru which relay CS is later to be energized will' be restoredby closure of contact cs2.

The deenergization of relay IV at the end of the phase A initialinterval has three effects. It dcenergizes relay AD through opening itsholding circuit at contact ivl3, contact CI!) of this circuit being openin cam' shaft position I. The relay AD operating circuit is independentof this holding circuit so relay AD continues to be responsive to 'Aphase detector actuations to extend the go signal display period duringthe following vehicle the same time prepares the circuit to the coil ofrelay CS from tube FA through the engaging oi armature ivlG with contactiv3 of relay IV, which circuit will be completed upon the closure ofcontact 0.82 as previously described. Another annature of relay IV, iv!0, substantially simultaneously separates from contact 5215 and engagescontact iv 4 thus substituting variable resistance AV for variableresistance AI in the charging circuit for condenser QA, and also makingcondenser QA subject to discharge thru contact ad3 of relay AD uponactuation of the A phase detector.

As a result of those described circuit changes caused by thedeenergization of relay IV a timer circuit is set up to time the vehicleinterval position of the A phase go signal display period, which timerincludes condenserQA, charging resistance AV, tube FA and relay CS. Thecharging circuit for condenser QA in this timer is the same as thatdescribed for the initial interval except that positive D. C., issupplied to armature z'vlil of relay IV thru contact i124 and resistanceAV instead of contact 2'05 and resistance AI.

Furthermore a discharge path for condenser QA is added at contact i114thru cam contact Cl, wire 32 and contact (1:13 of relay AD thence tonegative D. C. power. This discharge path is complete-d upon eachtrafilc actuation of the A phase detector, thru the energization therebyof relay AD and the consequent closure of contact (1113. This operationis the means by which A phase trafiic extends the A phase gosignalperiod during the vehicle interval portion of this period.

During the A phase vehicle interval period condenser QA is connectedwith tube FA and relay CS thru a circuit starting at negative D. C.power thence to condenser QA, thru wires 26 and 30 to tube FA, toarmature ivlfi and contact 223 of relay IV, wire 33 to contact cs2, tocoil of relay CS.

From the other side of relay CS coil there are four parallel paths anyone of which will, if completed, permit condenser QA to discharge thruthe coil of relay CS when tube FA becomes conducting. One of these whichincludes wire 34 and contact CIB is completed by closure of contact Cl 9in cam shaft positions 2, 4, and 6, the warning signal display positionsso that this timer will be effective to time the warning signal displayperiod as will be discussed later.

The other three of the four circuits are individually efiective toprepare an operating circuit for relay-CS which will be completed iftube FA becomes conducting during the vehicle interval portion of a gosignal period. Each of these three circuits includes in series a 'camcontact and a contact of one of the relays AD, BD, or CD, each of whichrelays will be energized if the right of way has been called, eitherby'trafjc actuation or v adjustment for normal reversion, to the phasewith which it is associated.

While the go signal is displayed in a phase, the operation of the relayresponsive to actuation of the traffic detector in that phase will beineffective to complete the particular relay CS energizing circuitwherein its contact is included because the cam contact in .each circuitis ar ranged to be open in the cam shaft position in which the go signalis displayed in the said phase. However, an operating circuit for relayCS always will be prepared in each vehicle interval period provided theright of way has been called to a phase other than that in which the gosignal is being displayed.

34, thence thru either contact bdl and cam contact CI'I or contact cd!and cam contact CH, depending upon whether the actuation was in phase Bor phase C respectively.

The completing of either of the last two circuits will cause relay CS tobe operable during the A phase vehicle interval when tube FA becomesconducting, i. e., when the last A phase vehicle has had suflicient timeto pass thru the intersection.

An actuation of an A phase detector during the A phase vehicle interval,which as previously mentioned will cause relay AD to operate, will notcomplete an operating circuit for relay CS since the cam shaft contactCl6 is open in the A phase go signal cam shaft position. Such anactuation will however, discharge condenser QA thru the previouslydescribed discharge circuit to extend the A phase go signal displayperiod.

When the right of way has been called to another phase and there iscontinuous traillc in the A phase which repeatedly resets the vehicleinter-val timer and so prevents this timer from acting, the right of waywill at the end of a predetermined period be transferred by action ofthe maximum timer.

If the equipment is adjusted to cause normal reversion of the right ofway to either the B or C phase, or if traflic is waiting on either ofthese phases at the beginning of the A phase go signal period themaximum timer will begin to time its period when the right of way isaccorded to the A phase. If there is no traffic waiting in the B or Cphase when the right of way is accorded to A phase and the equipment isnot adjusted to automatically accord the right of way to either phase Bor phase 0, the maximum timer will not begin to time its predeterminedperiod when tube FE and relay BS. Condenser QB is charged thru adifferent variable resistance when timing the maximum period in eachphase so that these periods can be independently adjusted. The chargingcircuit effective in cam shaft position 1, the A phase go signal displayposition, starts at D. C. plus power and includes variable resistanceAM, wire 35 leading to contacts in and 0014 which are connected inparallel, thence thru wire 36 to contact 026 and wire 31 to condenserQB, thence to D. C. negative power.

Cam contact C26 is closed in cam shaft position 1, hence if there is anautomatic call due to normal reversion or a traflic call for the rightof way in either phase B or phase C the maximum timer charging circuitwill be completed thru contact bdl or cdl. When condenser QB is chargedto the breakdown voltage of tube FB' it will discharge thru tube FB, thecoil of relay BS thence thru wires 38 and 39 to condenser QB.

- Relay BS will thereupon operate.

It can be seen from the foregoing discussion of the vehicle intervaltimer circuit and the maximum timer circuit, that neither of thesetimers can operate to move-the cam shaft out of a go signal positionunless trafllcv in another phase or an adjustment for automaticreversion thereto requires the transfer of the right of way. Hence. inthe absence of any call for the right of way on another phase, the camshaft will remain in positions 1, 3, or 5, with right of way accorded tophas A, B, or C respectively, until a right of way call occurs onanother phase.

The operation of either the vehicle interval timer or the maximum timerin response to such a call when the cam shaft is in position 1 willcause it to move into position 2, the phase A warning signal position.The vehicle interval timer accomplishes this thru closure of contact cslof relay CS which closure completes a circuit from negative A. C. powerthru wire 39, contact as! to solenoid S thence to A. C. plus power. The

solenoid will thereupon be energized and its core.

will be drawn in. At the end of the solenoid stroke contact sl will beclosed to complete a discharge circuit for condenser QA including wires25, 26 and 21 and resistance RA. Relay CS will thereupon be deenergizedthus opening contact csl which will deenergize the solenoid coil. Thesolenoid core will then return to its unoperated position and, in sodoing, move the cam shaft'into position 2.

If conditions are such that the maximum timer operates it will completethe solenoid coil circuit by closure of contact bsl of relay BS thusenergizing the solenoid and causing its core to be drawn in. At the endof the solenoid stroke contact 32 will be closed thereby dischargingcondenser QB of the maximum timer thru wires 39, 38, 40 and 4| andresistance RB, whereupon relay BS will be deenergized and will opencontact bs4 thus deenergizing' the solenoid the core of which willreturn to'its unoperated position and in so doing move the cam shaftinto position 2.

It has been stated that the maximum timer automatically puts in a callfor the return of the right of way to a lane when it acts to terminate aright of way period thereon. With respect to phase A this automatic,return call is put in by operation of relay AD which is accomplished asfollows.

When relay BS of the mardmum timer operates it closes contact bsl which,with the cam shaft in position 1, completes a circuit energizing relayAD. This circuit starts at negative A. C.

power and includes wire 62, contact 7'5, cam

contact C8, contact bsl, to coil of relay AD thence thru wire 44 to A.C. plus power. This circuit will be complete since relay J is, as hasbeen explained, deenergized under the prevailing conditions. Contact 1'5is therefore closed. Also cam contact C8 is closed in cam shaft position1, thus completing the above described circuit.

The opening of contact bsl as the solenoid returns to its unoperatedposition will open this circuit but relay AD will continue to beenergized thru a. holding circuit starting at negative A. C. power andincluding wire 45, contact iv|3 of relay IV, wire 66, contact adl, thecoil of relay'AD, and wire 44 which connects to A. '0. plus power. Itwill be noted that in the abovedescribed holding circuit contact ivlilisparalleled by cam contact Cl which is closed in cam shaft positionsB,4 and 5. This circuit will therefore remain complete to keep relay ADenergized until the next phase A vehicle intervalv period starts.v

At the beginning of the phase A vehicle interval, as explained before,relay IV is deenergized thus opening contact ivl3. Since contact Cli isopen during the A-phase go signal period this holding circuit willbecome incomplete and thus cause relay AD to be responsive to actuationof the A phase detector during the vehicle interval portion of the phaseA go signal period.

When the cam shaft solenoid is energized'by either the vehicle intervaltimer or the maximum A timer preparatory to power.

' warning signal AYS moving-the cam shaft from position 1,'the phase Ago signal display position, into position 2, the phase A warning signalposition, relay IV is energized by closure of solenoid contact 33 whichcompletes a circuit from negative A. C. power thru wire 42, to contact33, wire 25 to the coil of relay IV thence to A. C. positive Uponoperation, relay IV completes a holding circuit for itself from negativeA. C. power thru wire 41 to contact cs3, wire as to" contact ivl to thecoil of relay IV thence to positive A. C. power. I

The operation of relay IV closes contact ivli thereby preparing thepreviously described holding circuit for relay AD which will keep relayAD energized if it is operated thru action of the maximum timer relay BSat this time or if it is subsequently operated thru an actuation of theA phase detector. a

Furthermore, while the solenoid is energized contacts sl and s2 are bothclosed thereby completing the discharge circuits for condensers QA andQB respectively thru resistances RA and RB, thereby deenergizing therelay, either .BS or CS, a contact of which is completing the solenoidenergizing circuit previously traced and preparing these condensers foruse in timing new intervals.

As the cam shaft enters position 2 the A phase go signal AGSisextinguished and the A phase is energized. Other signal changes whichoccur as the cam shaft enters position 2 depend upon whether the rightof way has been called to the B phase or to the C phase,

but if, as assumed, the right of way is to be, accorded next to the Bphase, the B phase stop signal BRS is extinguished and the B phasewarning signal BYS is energized as the cam shaft moves into position 2.Under the above circumstances no signal change occurs in the C or Dphase at this time. With respect to relays the following 'conditionsprevail.

Relay J will not be energized as has been previously explained. RelayAG, which was ener gized in position 1 thru a previously describedcircuit, will remain operated in position 2 since contact C1 is closedin both of these cam shaft positions and contact 9'9 remains closed dueto .the i'act that relay J remains unoperated.

Relay AY will be energized, when the cam shaft has moved into position2, thru the circuit starting at positive A. C. power and including wire48; the coil of relay AY, wire 49, contact C24, wire 50, contact 7'6 ofrelay J which, thru member 9'1 and wire 55, connects to negative A. C.power.

When relay AY operates, contact 11 15, which is included in one of thethree previously described energizing circuits for relay J, is closed,but as previously mentioned does not energize relay J because thiscircuit includes contact bdii of relay BD which contact is open due tothe fact that relay BD was energized to call the right of way to B phaseand remains energized until the vehicle interval, portion of the B phasego signal period is initiated.

When the right of way is being transferred from phase A to phase B theoperation 'of relay AY which always causes the operation of relay AYX'inorder to energize the A, phase warning signal, also causes the operationof relay BYX in order to energize the B phase warning sigrial. Thecircuit by which relay AYX is so energized starts at'negative A. C.power-and includes wire 5!, contact 0412, wire 52, the coil of relay AYXand wire 20 which connects with positive A. 0. power. The circuit bywhich relay BYX is energized starts at negative A. C. power andincludeswire 5|, armature 1'") and contact 12 of relay J, contact a114, wire 53,the coil of. relay BYX and wire positive A. C. power.

The operation of relay AYX extinguishes the A phase g'o signal AGS bydisengaging armature ayxl from contact at and energizes the ,A phasewarning signal by causing armature .ayxl to engage contact ayzc2.

20 which connects with;

The operation of relay BYX extinguishes the" B phase stop signal BRS bydisengaging armature byxl from contact M23 and energizes the B phasewarning signal BYS by causing armature byml to engage with contactbyx'2.

The timing of the A "phase warning signal period is accomplished by atimer including condenser QA, tube FA and relay CS. The charging circuitfor condenser QA in this period starts at positive D. .C. power andincludes wire 54, contact ay'l of relay AY, which relay it will beremembered is energized in cam shaft position 2, variable resistance AW,wire 26, condenser QA which connects with negative D. C. power.

The duration of this period can be regulated by adjusting variableresistance AW to regulate In this cam shaft position contact C3I is open1 to prevent condenser QA and tube FA from operating relay AS. Theoperation of relay CS energizes, thru a previously describedcircuit,'the solenoid S which operates to move the cam shaft on intoposition 3, the 13 phase go signal position. As the cam shaft moves intoposition 3 the phase warning signal. and the B phase warning signal areextinguished. The A; phase stop signal and the B phase go signal areenergized at this time. No signal changes occur in the C or V D phases.

The foregoing signal display changes are brought about by thedeenergization of relays AY, AYX, BYX and AG and by the energization ofrelay BG.

The circuit changes which occur as the cam shaft moves into position 3and which cause the signal control relays to assume the above mentionedconditions are as follows. As the cam shaft moves into position 3 relayAY isdeenergized thru the opening of its previously described circuit atcontact C24. The holding circuit for relay AY which includes contactC30,

wire 55, contact ayl and armature i8 is'open at armature 7'8 since relayJ is unoperated as has been previously pointed out.

Relay AYX is deenergized thru the opening oi contact ay2, and relay BYXis deenergized thru the opening of contact ayl. Relay" AG is deenergizedthru the opening of cam contact CI and contact ayG which leaves noconnection from the coil of relay AG to negative A. C. power.

Relay BG is energized thru the closure of cam contact C9which-completes'the circuit starting at negative A. C. power andincluding wire 5| and I contact 1'9, wire 22, contact C9, the coil ofrelay BG and wire 20 which connects with positive A. C. power.

The phase A warning signal AYS is extinguished when armature ayml.disengages from contact ayzrZ. The phase A stop signal ARS is energizedwhen armature ayxl engages with contact ayr3 and armature agl engageswith contact ag3. The phase B warning signal BYS is extinguished whenarmature byzrl disengages from contact byzrZ, The phase B go signal BGSis energized when armature byml engages with contact byx3 and armaturebgl engages with contact 1292.

The B phase g0 signal period is divided into an initial intervalfollowed by the vehicle interval periodjust as was the phase A go signalperiod. The initial interval is timed by condenser QA, tube FA and relayAS which cooperate just as they did in the A phase initial interval,theonly difference .being that the charging circuit for condenser QAincludes cam contact C4,

armature ivll, contactiv'l and variable resistance BI in place of thecorresponding cam contact C2, armature ivll), contactivB and variableresistance AI which were included in phase A initial interval timingcircuit. This su titution is made so that the timing of the initialnterval can "be independently adjusted in the different phases.

'At the end of the phase B initial interval relay AS operates just as itdoes at the end of the w phase A initial interval and. deenergizes relayIV by opening the relay IV holding circuit at condischarge circuit forcond nser QA is prepared which will be completed to 'scharge condenserQA thru the closure of contact bd3 of relay BD upon actuation ofthe Bphase detector by which detector it will be remembered relay BD may beenergized. The above circuit starts at negative power and includes wire'55, contact 11113, wire 56, contact C3 thence to contactivB, armaturez'vl I,

contact C4, wire 26 to condenser QA thence back to negative power bywire 21. This is the means by which the B B phase go signal perio When,in the absence of further B phase traflic, condenser QA charges to .thebreakdown voltage of tube FA,'this tube will become conducting andcomplete the previously described circuit between condenser QA and relayCS which includes tube FA, armature ivlG, contact, 2'03, wire 33 andcontact as2. If there were no call for the right of way on either theAor C phase, relays AD and CD being consequently deenergized, there wouldbe no circuit from the coil of relay CS to nega.

tive A. C. power, each one of the four possible circuits previouslytraced being open at some point, one of them open at contact ad2,another I operate and the right of way would remain onat 0112, athirddpen at contact Cl! and the fourth open at contact CIQ. Hence, relay CSwould not the Blphase until a call to another phase completes one of theabove described circuits which would permit condenser QA to dischargethru relay CS and operate the same to move the cam phase traflic extendsthe' during the phase A vehicle interval period which has beendescribed. If there is no call for the phase B vehicle interval periodjustas it does right of way on another phase the charging cir- 1 cuitfor, condenser QB of this timer will be incomplete since both contactsad5 and ed! in the circuit eifective in cam shaft position 3 will beopen.

The maximum timer condenser charging cir- 4 cuit for phase B includescontact C21, contacts M15 and cd5 connected'in parallel, wire 51 andvariable resistance BM in place of the charging circuit of this timerduring the A, phase vehicle interval period.

A call for the right of way on the A chase will start-the timing of themaximum ,....iod thru completing this charging circuit at contact adi. Aphase'C call for the right of way will do'the same thru closure ofcontact c115.

If the maximum timer relay BS operates it moves the cam shaft into.position 4 just as it moved it into position 2 which operation haspreviously been described. Moreover, the operation of the maximum timerin. cam shaft position 3 automatically puts in a. call for the return ofthe right of way to phase B thru energizing relay BD due to the closureof contact D82 just as in cam shaftposition 1 is energized relay AD thruclosure of contact bsl, The closure of contact bs2 completes anoperating circuit for relay BD which includes wire 44, relay BD,contacts bsZ,

and CH), wire 43,-contact 7'5, wire 42.

The signal changes which occur as the cam shaft moves into the B phasewarning signal position 4 depend upon; whether the right of way has beencalled to phase A or phase C. Since in the present portion urthedescription it is assumed that the right of way is next to be accordedto the C phase, the following signal dis-- play changes will occur. asthe cam shaft enters position 4: v r

The B phase go signal BGS, the 'D phase go signal'DGS, and the, C phasestop signalCRS 1 will be extinguished; The D'phase trafiic must bestoppedflit',willfbejenimbered, when the C addition to the abovechanges, the B phase warnand the D phase warning signal DYS areenergized in cam shaft position 4 when the right 01:; fre'm phase B tophase way is being transferred C. To bring about the above changes insignal display in this can: shaft position relays BY, BYX and CYX willbe energized;

Relay BY will be energized thru the closure of contact C22 whichcompletes a circuit starting at positive A. C. power and including wire48,

the coil of relay BY, wire 58, contact C22, wire 59, contact 7'6 and'm'ember 7'1 of relay J which connects to negative A. C.- power. The.consequent operation of relayBY clauses the completion of circuitsenergizing relays BYX and CYX as follows: 1

Relay BYX is energized thru the closure of contact 12 2 which vcompletesthe circuit start-' B5 phase trafllc isQto be given the right of way. In1 gization of relay BY will open the pr 1 33 at positive A. C. power andincluding wire a, the coil oi relay BYX, wire 83, contact by! and wire5|, which connects with negative A. C.

wer.

Relay CYX is energized thru the closure of contact M! which completesthe circuit starting at positive A. C. power and including wire 20, thecoil 0! relay CYX, wire 60, contact by, contact {l2 andiarmature iii ofrelay J which connects-with negative A. C. power.

The B phase go signal BGS is extinguished by the separation of armaturebyrl from contact burl. The B phase warning signal BYS is energized bythe engaging oi armature burl with contact byxZ. The 0 phase warningsignal CYS and the D phase warning signal DYS are energized by theengaging oi armature cyrl with contact cyzZ. The C phase go signal C63and the D phase stop signal DRS are extinguished by the separation ofarmature cyxl from contact 0 112. No signal changes occur in the Aphase.

The B phase warning signal period is timed by condenser QA, tube FA andrelay CS which cooperate to do this Just as theytimed the A phasewarning signal period. The charging circuit for condenser QA in the B.phase warning signal period however, includes variable resistance BWand contact by! which contact is closed upon the previously mentionedoperation of relay BY.

At the end of the B phase warning signal period relay CS will operate asit does at the end of the A phase warning signal period. This will causethe solenoid S to move the cam shaft into position 5, the phase C gosignal position.

As the cam shaft moves into position relay -BY will be deenergized bythe opening of contact 022 which is included in the previously tracedenergizing circuit for this relay. The deenere viously traced energizingcircuits for relays BYX and CY! at contacts by! and by! respectively.

. In addition to the above changes relay BG will be deenergized thru theopening 0! contact C9 since its holding circuit also is open at contactbyflandrelayCGwillbeen'ergized thruthe closure 01 contact C whichcompletes the circuit including wire 5|, contact i8, wire 22,contactCll, coiloirelayCGand wire.

The above outlined changes in relay position cause signal displaychanges as follows. The B p ase p signal BBS is energized by theengaging of armature bt rl with contact byx3 and the engaging oiarmature bgl with contact I293. The phase B warning signal BYS isdeenergized thru the separation of armature bi/xl from contact but. Thephase C warning signal CYS and the D phase warning signal DYS aredeenergized by the separation oicarma cyrl from contact c 12. The phaseC go si CGS and the phase I) stop signal DRS are energized by theengaging o1 armature 'cyxl with contact (21/13 and the en ag g oiarmature col with contact e03,

The C phase go signal period in position 5 is similar to thecorresponding periods for A and B phases and is comprised oi an initialinterval andvehicle'interval which are timed by condenser QA and tube FAin the manner described above for the A and B phases. The chargingresistance for the initial interval portion is variable resistor CI, andfor the vehicle interval, resistor CV.-

Maximum timing condenser QB is charged thru a corresponding appropriatecircuit including resistor CM.

If at the termination of thevehicle interval timer period there were nocall for transfer of taneously the C phase and the D right oi way from Cphase to one of the other phases, none of the described circuits fromrelay CS coil to negative would be completed and relay CS consequentlywould not operate to advance the cam shaft from position 5 until such acall should be received. In the present portion of this descriptionhowever, it is assumed that there is traillc in all the lanes and thatrelay AD is energized. Accordingly, either upon operation of relay CS bycompletion of the vehicle interval timer period or upon operation ofrelay BS by comple tlon oi the maximum timer period the solenoid isadvanced to position 6, the phase C warning signal period.

As the cam shaft moves into position 6 the phase C go signal 068 and thephase D stop signal- DRS are extinguished. Substantially simulphasewarning signals CYS and DYS are energized and, assuming that the rightof way has been called to the A phase, the A phase warning signal AYSwill be energized. These signal display changes are -brought about bythe energization of relays CY,

CYX and AYX.

Relay CY is energized due to the closure of contact C23 which completesa circuit starting at positive A. C. power and including wire 48, thecoil of relay CY, wire 62, contact C23, wire 63, contact is and contactarmature 7'! of relay J which connects with negative A. C. power.

The operation of relay CY causes the energizetion of relays CYX and AYX.The circuit for relay CYX starts at positive A. C. power and includeswire 20, the coil of relay CYX, wire 60, contact c112, and wire 5|,which connects with negative A. C. power. The circuit thru which relayAYxis energized starts at positiveA. C. power and includes wire 20, thecoil of relay AYX, wire 52, contact c114, contact ii: and armature 10 ofrelay J, which'connects with negative A. C. power.RelayCGremainsenergizedincamshaitposn tlon 6 thru the same circuit whichenergized it in position 5.

Thechangesinsignaldisplayas thecamshait enters position 6 are broughtabout as follows: The A phase stop s gnal ARS is deenergined by thedisengaging oi armature ayxl from contact aye-3.- The A phase warningsignal AYS is enersized by the engagement of armature am! with contactayxl.

The C phase go signal CGS and the D phase stop signal DRS aredeenergized by the separation of armature cyzl from contact c1113. The Cphase and the D'phase warning signals CYS and DYS are energized by theengagement of armature c'yxl with contact cy'x2.

The C phase warning signal period is timed by condenser QA, tube-EA,and.relay CSlwhich cooperate Just as was previously described in thediscussion of the A and B phase warning signal periods except that adifl'erent charging circuit is arranged for condenser QA so that the Cphase warning signal period can be timed independently oi the. othertwo. This circuit is completed to begin the timing of the C phasewarning period as the cam shalt moves intoposition 6.

The operation of relay CYR, which as mentioned, takes place at thistime, completes the phase C warning signal period timing circuit byclosure oi contact cpl, thereby completing the condenser QA chargingcircuit which starts at positive D. 0. power and includes contact c111,variable resistanceCW, wire- 26, condenser QA and wire 21, whichconnects with negative D. C. power. The timing of the phase C warningsignal is adjustable thru the regulation of variable resistance CW.

When the phase C warning period is over relay CS operates in accordancewith previous explanation and causes the solenoid to move the cam shaftinto position 1, the phase A go signal position. As the cam shaft entersposition 1 relay CY is deenergized by the opening of contact 023. Thedeenergization of relay CY causes the opening of contacts c112 and 0314which cause the deenergization of relay CYX and AYX, the circuits ofeach of which includes one of these contacts. Relay CG is deenergized bythe opening of contact CH and relay AG is energized by closure ofcontact CT.

The above mentioned changes in relay positions extinguish the A phase, Cphase and D phase warning signals, the circuits for which havepreviously been traced. Inaddition, the C phase stop signal, the A phasego signal and the D phase go signal are energized which returns thesystem to the condition prevailing at the beginning of this step by stepdescription.

It has been previously stated that if there is no call for the right ofway registered in the phase next in the normal order of progression andthere is a call for the right of way in the phase not next in the normalorder of progression, this equipment will operate to transfer the rightof way to the phase not next in the normal order of progression withoutany signal display change in the omitted phase.

Operation of the system to transfer the right of way from phase Adirectly to phase C in response to a call for'the right of way therefromwithout any signal display change in phase B wherein no right of waycall has been registered will now be described.

Assume that the ight of way has just been accorded to phase A, cam shaftin position 1, that there is no call for the right of way in phase B andthat'there is such a call in phase C. Relay BD will not be energized dueto the absence of a phase B right of way call. Relay CD, having beenenergized when the right of way was called to phase c. will still benergized thru its holding circuit which includes contact call and Gil.

The A phase 80 signal AGS and the D phase go signal DGS are energized.The B and C phase stop als BRS and CR8 are also energized. The circuitcondition prevailing to bring about the abpve signal display combinationis identical with that explained in a previous consideration of thephase A go signal period.

At the end of the phase A initial interval relay A8 of the initialinterval timer will operate to terminate this interval and to start thephase A vehicle interval exactly as described in the explanationpreviously given in connection with the transfer of the right of wayfrom phase A to phase B.

The phase A vehicle interval is timed as has .been also previouslyexplained. The particular circuit effective to supply negative D. C.power to relay CS 0! the vehicle interval timer under the presentcircumstances is that one including cam contact CH and contact cd2 ofrelay CD which relay is energized due to the phase C call for the rightof way.

The phase A go signal period can be terminated by action of either thevehicle interval timer or the maximum interval timer exactly asexplained before. The particular circuit thru which the maximum timercondenser QD is charged under the present circumstances includes camcontact C26 and contact cdl of relay CD. If the phase A go signal periodis terminated by the maximum timer a phase A return right of way call isautomatically put in in accordance with the previously explained method.

As the cam shaft, at the end of the vehicle interval portion of thephase A go signal period is moved into position 2 relay AY is energizedjust as explained previously. The energization of relay AYX follows atonce as has also been previously explained.

Due to the fact that the phase B go signal period is to be omitted underthe present circumstances relay J will be energized by the operation ofrelay AY. It will be remembered that relay J remained deenergized whenthe right of way was being transferred from phase A to phase B.

The circuit thru which relay J is energized starts at positive A. C.power and includes wire IS, the coil of relay J, wire I9, contact 0115of relay AY, wire l8, back contact bdS of relay BD, which relay it willbe remembered is not energized, and wire II, which connects withnegative A. C. power. As soon as relay J operates contact 12 closes thusproviding a path independent of contact bd6 thru which relay J willcontinue to be energized if a phase B tramc actuation occurs whichactuation would energize relay BD thereby opening contact bdfi includedin the relay J energizing circuit.

The functions of relay J, which as mentioned operates at the beginningof the wa n signal period when the normally next phase go signal periodis to be omitted, are as follows:

Relay J, when operated, causes the signal display changes which wouldnormally occur in the phase being omitted to take place in the phasebeyond to which phase the right of way is being transferred. Itaccomplishes this by changing the connections among the signalcontrol'relays as will be later explained in detail.

Relay J, when energized, completes a special charging circuit for themaximum timer condenser QB which makes this timer effective to rapidlystep the cam shaft thru the positions in which the signal indications tobe omitted normally occur.

Relay J, when operated, makes effective circuits to keep the severalsignal control relays from being disturbed while the cam shaft is beingrapidly stepped thru positions in which these relays would normallychange from an energized condition to one of deenergization or viceversa.

Furthermore, relay J, when operated, opens the automatic return callcircuit associated with the maximum timer so that this timer will notput inan automatic right of way call for the phase being omitted when,operating as the special rapid stepping timer, it moves the cam shaftout of the position wherein the go signal normally is displayed to theomitted phase.

from contact ill thereby opening the previously traced circuit overcontact 712 by which relay AY, upon operation normally energizes relayBYX which in turn energizes the phase B warningsignal. Hence relay BYXwill not operate under the prevailing circumstances and consequently thephase B warning signal BYS will not be energized. The engagement ofarmature 1' ill with contact ill completes another circuit by whichrelay CYX is energized when relay AY is operated. This circuit starts atnegative A. C. power and includes wire 5|, armature alfl, contact ii i,contact 0113, the coil of relay CYX and wire 2Q,

which connects with A. C. positive power.

The energization of relay CYX causes the energization of the phase C andthe phase D warning signals CYS and DYS thru a circuit previouslytraced. Hence the warning signal in the omitted phase, phase B in thiscase, is not energized but the warning signal in the phase beyond, PhaseC in this case, is energized simultaneously with the phase A warningsignal.

The second of the four mentioned functions of relay J that of completinga special low resistance charging circuit for condenser QB of themaximum timer is accomplished by closure of contact 7'4 which, withrelay AY operated as is now the case, completes the circuit starting atpositive D. C. power and including contact 7'4,

low resistance JR, wire 64, contact (.1118, wire 65, contact C21, wire31', condenser QB, which is connected-to negative D. Cw power. Thru thiscircuit condenser QB of the maximum timer will be charged in a shortperiod, on the order of one fourth of a second, to the breakdown voltageof tube F'B whereupon relay BS will operate and cause the solenoid tomove the cam shaft into position 3. While the solenoidis operated toaccomplish this cam shaft movement, contact s2 closes dischargingcondenser QB, thus causing relay BS to be deenergized and so permittingthe solenoid to return to its unoperated condition during which.movement, as previously pointed out, it moves the cam shaft intoposition 3.

Condenser QB is immediately recharged thru the special low resistancecharging circuit and consequently the cam shaft is moved on intoposition 4 by the maximum timer relay about one quarter of a secondafter it was moved into position 3. In cam shaft position 4 this speciallow resistance charging circuit for condenser QB is made incomplete atcontact C21 which opens in this cam shaft position.

As the cam shaft moves into position 4 the warning signal period timercomprising condenser QA, tube FA and relay CS begins to time the normalphase A warning signal period at the end of which the cam shaft will bemoved into position 5, the phase C go signal position, in the usualmanner which has been previdusly described.

The third mentioned function of relay J, that of preventing the signalcontrol relays from be ing disturbed while the cam shaft is beingstepped rapidly thru the phase B go signal position, requires thatduring this transition period relays J, AG, AY, AYX, and CYX which wouldnormally become deenergized in cam shaft position 3 be kept energizeduntil the cam shaft moves into the phase C go signal position 5. This isaccomplished by special holding circuits which are completed by contactsofrelay J when that relay operates aswill nowsbe explained.

The holding circuits of every one of the above mentioned relays willremain complete so long as in theoperating relay AY remains operated,hence relay AY is the determining factor in the situation. Relay AY, itwill be remembered, operates upon closure of cam contact C24 as the camshaft moves into position 2. The operation of relay J follows by closureof contact 15 as has been explained.

The above mentioned operation of relay J completed a holding circuit forrelay AY which starts at negative A. C. power and includes wire 66,contact 7'1 and armature 7'8 of relay J, wire 61, contact ayi, wire 55,cam contact C30, wire 49, the coil of relay .AY and wire 48 whichconnects with A C. positive power. It will be noted that coni6 and 7'1,the first of which is included circuit of relay AY and the secondofwhich is included in the holding circuit of relay AY, are bothassociated with a common armature 9'8 in such a way that the holdingcircuit of relay AY invariably completed before the operatingcircuit---thereof is broken. This arrangement provides that relay AY,which operates before relay J, shall not be deenergized when relay Joperates.

The described holding circuit for relay AY remains complete until theopening of cam contact C30 as the cam shaft enters position 5. From theforegoing it can be seen that relays AY and J will remain energizeduntil the cam shaft reaches position 5, the. phase C go signal position.Relays AYX and CYX, of which the energizing circuits have been traced,will remain energized as contacts of relays AY and J control theenergizing circuit of relays AYX and CYX.

Relay AG, which is energized in cam shaft po-.

sitions 1 and 2 and which normally is deenergized in cam shaft position3, will, under the prevailing circumstances remain energized until thecam shaft reaches position 5, power for this relay being supplied thru aholding circuit therefor which circuit includes contact ayB of relay AY,which is energized until position!) is reached.

The fact that relay AG remains energized in cam shaft positions 3 and 4is of no significance with the apparatus adapted as shown in Fig. 3, togive the signal sequence G, A, R, A, G. However, with the apparatusadapted to give the signal sequence G, A, R, R, G, as shown in Fig. 4,the energization of relay AG in cam shaft positions 3 and 4, asdescribed above, has a significance which will be pointed out later whenthe adaptation of the apparatus to give the G, A, R, R. G signalsequence is considered.

In addition to the sary function of relay J is to prevent theenergization of relay BG which normally occurs when the cam shaft is inpositions 3 and 4, which energization would cause the display of thephase B go signal in cam shaft position 3. The operation of relay Jprevents relay BG from operating by opening the previously tracedenergizing circuit for the latter at contact 19.

The fourth mentioned function of relay J, that of preventing the settingup of an automatic call for the return of the right of way to the Bphase as the cam shaft is moved out of position 3 by the maximum timeracting as a special rapid stepping timer.

This is accomplished by the opening of the previously traced automaticrecall circuit at contact 1'5 of relay J which relay it will beremembered is operated under the prevailing circum- From. the abovediscussed foregoing, a further neces-' can be seen that, when the rightof way is to be transferred from phase A to phase C, the cam shaft, whenthe phase A go signal period is over,

' will be rapidly stepped thru positions 2 and 3.

and will then remain for a normal phase A warning signal period, timedby the phase A warning signal period timer, in cam shaft position 4, atthe end of which period the cam shaft will be moved on into position 5wherein the go signal is displayed in phase C and the stop signal isdisplayed in all other phases.

While'the cam shaft is in positions 2, 3 and 4, as above mentionedrelays AY, J, AG, AYX and CYX will all be energized. The signal displayduring this period will consequently be as follows:

The phase A warning signal AYS will be energized by engagement ofarmature ayxl with contact aym'i.

The phase C and the phase D warning signals CYS and DYS will beenergized by the engagement of armature cyml with contact 011112.

'The phase 3 stop signal BRS will remain energized thru its previouslytr aced circuit inasmuch as relays BYX and BG are both deenergized asexplained above.

When the cam shaft reaches position 4, as previously mentioned thenormal phase A warning signal timer times a normal phase A warningsignal period at the end of which the cam shaft in the usual way ismoved on into position 5. As the cam shaft enters this position relay AYis deenergized thru the opening of its holding circult at contact C30.This causes the deenergization of relays J, AG, AYX, CYX, all of whichrelays depended, as has been explained, upon relay AY contacts for theirenergy. This change complates the transfer of the right of way fromphase A directly to phase C.

The operation of the apparatus to transfer the right of way from phase Bdirectly to phase A omitting phase C which operation is similar to thatjust described in connection with the transfer of the right of waydirectly from phase A to phase C, will now be explained briefly. 1

Assume that, while the go signal is being displayed in phase B, theright of way is called to phase A and there is no call for the right ofway on phase C. Under this condition the transfer of the right of wayfrom phase B to phase A, with no signal display changes in phase C or D,will be accomplished as follows.

The movement of the cam shaft from position 3, the B phase go signalposition, to position 4, the B phase warning signal position, will becccasioned by the normal operation of either the vehicle interval timeror the maximum interval timer exactly as previously described.

As thecam shaft moves into position 4 relay BY will be energized due tothe completion of its 60 previqusly described operating circuit byclosure of contact C22. Relay J will thereupon be energized by closureof contact by5 which completes the circuit including the said contactby! and contact 0116, the last named contact being closed because relayCD is not energized, there having been no phase C right of way call toenergize relay CD.

The closure of contact i3 which parallels contact cdB will prevent relayJ from being deenergized by a subsequent phase C right of way call justas contact 9'2 similarly provided protection for this relay againstdeenergization by B phase tramc actuations when the right of way was being transferred from phase A to phase C.

The operation of relay J completes a 19W resistance charging circuit forthe maximum timer condenser QB similar to that described in connectionwith the transfer of the right of way from phase A directly to phase 0.

This circuit which includes contact '4, low 5 resistance JR, wire 68,contact mm, wire 69, cam contact C25 and wire 31, remains intact in camshaft positions 4 and 5 and so causes the maximum timer to operate tomove the cam shaft out ofeach of these positions about one quarter of asecond after its entrance therein. As the cam shaft moves into position6 this special low resistance charging circuit is rendered incompletethru theopening of contact C25 and is therefore not effective to causethe cam shaft to be moved out of position 6.

The previously described circuit thru which the operation of the maximumtimer in cam shaft position 5 would normallyenergize relay BB in orderto put in a call for the return of the right of way to phase B is opendue to the opening of contact 7'5. Therefore no such return call is putin under the prevailing circumstances when the maximum timer relay CSoperates to movethe cam shaft out of position 5.

The operation of relay J also completes a hold ing circuit for relay BYsimilar to the holding circuit previously described in connection withrelay AY. This holding circuit for relay BY includes cam contact C28,contact byl, armature i8 and contact 9'1, and will remain intact in camshaft positions 4, 5 and 6, thus insuring that relay BY and also thesignal display control relays, BG, BYX and AYX, which under theprevailing circumstances are energized thru contacts of relay BY willremain energized contin-' uously from the entrance of the cam shaft intoposition 4 until it leaves position 6, the phase C warning signalposition.

The circuit thru which relay BYX is energized as mentioned above, hasbeen previously described. It includes contact of relay BY. The circuitthru which relay AYX is energized as mentioned above, includes contactbut, contact ill and armature ill) of relay J. 45

Relay BG is maintained energized in cam shaft positions 5' and 6 byclosure of contact byi of relayBY. This continued energization of relayBG has no significance with the apparatus adapted to give a signalsequence G, A, R, A, G, which adaptation is now being considered. Itdoes, however, have a significance if the apparatus is adapted to givethe signal sequence G, A, R, R, G which will be pointed out later whenthe adaptation of the apparatus to give the latter signal sequence isconsidered.

Due to the fact that relays AYX and BYX under the prevailingcircumstances are energized in cam shaft positions 4, 5 and 6, the A andB phase warning signals AYS and BYS, the cir- 60 cuits for which havepreviously been traced, will both be energized continuously from thetime the cam shaft enters the B phase warning signal position 4 until-itleaves position 6, the 0 phase warning signal position,

The 0 phase go signal CGS which is normally energized when the cam shaftis in position 5, will not under the prevailing circumstances beenergized while the camshaft is in position '5 since relay CG, a contactof which is included in the phase C go signal circuit, will not beenergized. Relay CG will not be energized due to the opening of contact1'9, which is included in ,its previously traced energizing circuit.

The Qphase and D phase warning signals which are normally energized whenthe cam shaft is in position 6 will not be so energized under theprevailing circumstances because relay CYX will not be energized, allthree circuits thru which this relay could be energized being open. Thecircuit thru which relay CYX is normally energized in cam shaft position6 which circuit includes contact era! of relay CY is open at thiscontact since relay CY is not energized under the prevailingcircumstances. The previously traced circuit thru which relay CY isnormally energized in cam shaft position 6 is open due to the separationof contact 1'6 from contact jl. Also, the previously traced circuit thruwhich closure of contact'byl of relay BY could energize relay CYX isopen due to the separation of armature y'lll from'contactiii. The onlyother circuit thru which relay CYX could be energized is open at contactor! since relay AY is not energized during the transfer of the right ofway from phase B to phase A. Therefore relay CYX is not energized andthe phase C and D waming signals are consequently not energized as wasmentioned. v

The fact that relays CG AND CYX do not operate causes the C phase stopsignal CRS, the circuit of which has been traced, to remain enerwhilethe right of way is being transferred from phase B directly to phase A.

The cam shaft will remain in position 6 for the normal B phase warningsignal period timed by the B phase' warningslgnal period timer thecircuit for which has been previously described, which circuit includestube FA, condenser QA, charging resistance BW and relay CS. This timeris made effective to time this period in cm shaft position 6 thru theclosure of contacts b111, C20, (182, 'and CIS.

When the cam shaft is moved from position 6 to position 1 by action ofthe phase B warning signal timer as mentioned; the described holdingcircuit for relay BY will be opened at cam contact C28. Relay BY willthereupon be deenergized and will cause relays BG, AYX, BYX, and J to bedeenergized thru the opening of contacts M6, M3, M2, and D respectively.

The phase A and phase B warning signals AYS and BYS'and the phase A stopsignal ABS are thereby extinguished and the phase A go signal AGS isenergized in accordance with the previously described condition normallyprevailing when the cam shaft is in position 1, the phase A go signalposition.

If. when the right of way is accorded to phase C there is a-- call forthe right of way on phase B and no call for the right of way on phase A,the right of way will be transferred directly from phase C to phase B,the stop signal remaining continuously displayed to A phase traffic.

The camshaft under the above circumstances will be moved .out ofposition 5, the C phase go signal positionhby normal action of eitherthe vehicle interval timer or the maximum timer which has beenpreviously explained.

As the cam shaft enters position 6, the C phase warning signal position.relay CY is energized as previously explained. Relay J thereuponoperates being energized thru the circuit including contacts 011! andM6, the latter contact being closed since there has been no phase Aright of way call to operate relay AD. Contact I closes in order to protect relay J against deenergization by subsequent phase A traillcactuations which would open contact adfl.

The operation of relay J completes a holding circuit for relay CY.thruthe engaging of armature 7'8 with contact 51. This holding circuitincludes contact i1, armature 18, wire 61, contact cyi, and cam contactC29. It will be remembered that the association of armature 18 withcontacts 7'6 and 1 is such that the holding circuit for relay CY will becompleted before the operating circuit for this relay is broken. RelayCY will therefore remain energized thru this holding circuit while thecam shaft is in positions 6, 1 and 2, being de-- energized when camcontact C29 opens which occurs as the cam shaft moves into the B phasego signal position 3.

Relay CG is held energized in cam shaft positions 1 and 2 thru contactc115 of relay CY. This has no present significance but is significantwith the apparatus adapted to give the G. A, R, R. G signal sequencewhich will later be pointed out.

Relay CYX is energized'by closure of contact cyl of relay CY. Thiscauses the extinguishing of the C phase go signal CGX, the D phase stopsignal DES and energizes the C and D phase warning signals CYS and DYS,the circuits for 'all of which have previously been traced.

Relay BYX is energized by closure of contact cm! of relay CY and theengaging of armature ill with contact jl l. The operation of relay BYXextinguishes the B phase stop signal BRS and energizes the B phasewarning signal BYS the circuits for which have been previously traced.

Since relays J CG, BYX and CYX are all energized thru circuits dependentupon contacts of relay CY. these relays will all remain energized untilrelay CY is deenergized, i; e., until the cam ing incomplete thepreviously traced circuit thru which relay AG would normally beenergized. Relay AG will therefore remain unoperated throughout thetransfer of the right of way from phase C to phase B.

Relay AY which would normally be energized in cam shaft position 2, theA phase warning signal position, will not be so energized under theprevailing circumstances since its previously traced operating circuitis open at contact 16.

Relay AYX will not be energized since one energizing circuit therefor isopen at contact a 2, another energizing circuit therefor is open atcontact b 13, of relay BY which relay is not energized during thetransfer of the right of way from phase C to phase B. The third circuitthru which relay AYX could be energized .is open at contact ill.

No change will therefore be madein the A phase signal display sincerelays AG and AYX which control the A phase signals have been 'shown toremain continuously deenergized shaft enters position 6 also completes alow resistance charging circuit for condenser QB of the" maximum timerwhich circuit includes contact 54, contact c118 and cam contact C26.

This circuit remains complete in cam shaft positions 6 and 1 and willtherefore cause the maximum timer to move the cam shaft out of positions6 and 1 about one fourth of a second after it enters them. In cam shaftposition 2 contact C26 of this circuit is open, thus rendering the maxi--mum timer inefiective as a quick acting timer to move the cam shaftoutof this position. 2 Moreover, the operation of .relay J causes con- 5tact 7'5 to open, thereby preventing relay BD-from being energized bythe maximum timer to put in an automatic call for the return of theright of way to phase B when this timer, operating as a special quickacting timer, moves the cam shaft out of the phase A go signal position1.

-.The cam shaft will remainjn position 2 for the normal phase C warningperiod timed by the previously discussed phase C warning signal timerwhich timer will be effective to do so due to the continued closure ofcontact cy'! of relay CY which relay it will be remembered remainsenergized under the prevailing circumstances until the cam shaft entersposition 3, the B phase go signal position.

When the cam is moved into position 3- by action of the warningsignalperiod timer the previously described holding circuit for relay CY isopened at contact C29. Thereupon relay CY I and also relays J, CYX, AYXand CG which were energized thru contacts of relay CY will all bedeenergized. In addition, relay BG will be energized thru its previouslydescribed circuit by closure of cam contact C9 and the-closure ofcontact '9.

The warning signals in phases C, D and B will thereupon be extinguished.The stop signal in phase C, and the go signals in phases B and D will beenergized. The circuits for all of thes signals have been previouslytraced.

The right of way is now accorded to phase B and consequently to phase Dalso. Further transfers of the right of way will be dependent upon therequirements of traffic and will take place in accordance with thedescribed operation of the apparatus,

It has been stated herein that the apparatus of the present invention iscapable of being adapted by slight circuit changes to give signalsequences other than the G, A, R, A, G sequence.

45 This is accomplished by changing the connections between the signalcontrol relays and the signals. Figure 4 shows the signal connectionswhich give a G, A, R, R, G signal sequence in each of the lanes.

50 Both of the above mentioned signal display sequences are in commonuse. Hence it is shown herein how the embodiment of the presentinvention can be adapted to provide either one of them.

Several other signal sequences can be provided by connecting the signalsto the signal control relays in different ways. The two adaptationsdepicted herein are shown primarily in order to demonstrate theflexibility of the apparatus with respect tosignal display sequence.

Figure 4 includes the signals in the several lanes,the signal controlrelays AG, BG, CG, AYX, BYX, CYX and two additional relays, DG andDY,'included to control the D phase signals; The energizing circuits for,these relays are shown in Fig. 3 excepting those of relays DG and DYwhich will be discussed later. Hence the conditions under which each ofthese relays, except DG and DY, will be" energized or deenergized, willbe the same in Fig. 4 as in Fig. 3. Considering the arrangement of therelay contacts and the two supplementary relays of Fig. 4 which areconnected,

. as indicated, to the structure of Fig. 3, the signal indications givenby the apparatus as shown in Fig. 4 will be asfollows:

75 When the cam shaft is in position 1, the A signal is normallydisplayed in phases A and D,

' armature cal with contactagi. The 13 phase go phase go signalposition, relay AG is normally energized and relay AYX is normallydeenergized as has been previously shown. Hence the phase A go signalAGS will be energized thru contact (1:123

and armature ayzcl of relay AYX and contact ag2 5 and armature agl ofrelay AG.

' Relays BG and .CG are normally deenergized when the cam shaft is inposition 1 as has been explained; hence the B phase stop signal BRS isenergized thru armature bgl and contact bg3 and the C phase stop signalCRS'is energized thru armature cgl and contact 093.

In Fig. 4 the D phase signals are controlled by relays DG- and DY. Thesetwo additional relays are needed because of the non-symmetry of thesignal sequence G, A, R, R, :G, which precludes the use of the phase Dsignal connections shown in Fig. 3.

It will be noted that relay DG is energized at all times when the phaseC stop signal is energized, since its energizing circuitis connected tothe positive side of the phase C stop signal circuit and includes wire70, the coil of relay DG and wire H which connects to A. C. negativepower.

Relay DY is connected in parallel with relay CYX thru its circuitincluding the coil of relay DY and terminal 12 which connects with therelay CYX circuit in Fig. 3.

With the cam shaft in position 1 relay DG will normally be energized andrelay DY will normally be deenergized. Hence the phase D go signal DGSwill be energized thru its circuit which starts at positive A. C. powerand includes armature dgl, contact dgZ, armature dyl, contact dy3. Thephase D stop signal circuit is open at contact (19,3 and the phase. Dwarning signal circuit is open at contact dy2.

From the foregoing discussion, it. is evident that when the cam shaft isin position 1 the go whereas the stop signal is normally displayed inphases B and C.

As the cam shaft moves into position 2, theA phase warning signalposition, relay AYX is energized, thereby extinguishing the A phase gosignal AGS by opening its circuit at contact owl and the A phase warningsignal AYS is energized by the completion of its cir'cuit thru theengaging of armature ayzl with contact ayxz'.

At the same time, as previously shown, if the right of way is next to beaccorded to phase B, relay BYX will be energized. However, this changewill not alter the signal display since armature byzl is not connectedto power due to the fact that relay BG is deenergized in cam shaftposition 2, which causes armature bgl to be separated from contact 1292,thereby disconne'ctingarmature byzcl from power.

The fact that relays BG and CG are normally deenergized in cam shaftposition 2 causes the B and C phase stop signals to remain energizedduring the A phase warning signal period which is in accordance with therequirements of the G, A. R, R, G, signal sequence.

-11, as it is now assumed, the right of way is next to be accorded tophase B, the cam shaft will,- upon leaving position 2, stop in position3, relays AYX, BYX and AG will thereupon all be deenersized and relay BGwill be energized as previously explained. Therefore, in cam shaftposition 3 the A phase warning signals AYS will be extinguished by theopening of its previously traced energizing I circuit at contact ayxi.The A phase stop signal ARS will be energized due to the engaging ofarmature cyxl ca Y contact n93.

signal BGS will be energized thru the circuit including contacts byxiand bg2.

.If, contrary to the above assumption, the right of way upon beingwithdrawn from phase A is next to be accorded to phase C, relays AYX.CYX

and DY will be energized when the cam shaft moves into the position 2,the A phase warning signal positions.

The energization of relays AYX and CYX has no effect on the signaldisplay since their armatures are not connected to power as pointed outabove in the case of relay BYX. The energization of relay DY which relayas'explained previously is connected in'parallel with relay CYX,extinguishes the phase D go signal DGS by opening its energizing circuitat contact-(i 13 and illuminates the phase D warning signal DYS by theengagement of armature dyl with contact (1112 which completes thecircuit starting at positive A. C. power and including armature dgl,contact dgl, armature dyl, contact dyZ.

It will be remembered that when the right of way is being transferredfrom phase A to phase It will also be remembered that the signal controlrelays remain in the same condition in cam shaft positions 2.3 and 4 anduntil the cam shaft moves into position 5. Hence the signal displaydescribed above will remain unchanged until the cam shaft reachesposition 5, the C phase go signal position.

As the cam shaft moves into the last named position relays AG, AYX, CYXand, consequently relay CY whichis connected in parallel with relay CYXare deenergized. At the sametime relay CG is energized. All of the abovechanges in relay condition have been previously explaincd. v

In consequence of these changes in relaycondition the A phase warningsignal AYS is extinguished by the opening of its circuit at contact caland the A phase stop signal ARS is energized by the engagement ofarmature aol with Furthermore; the phase C warning signal CYS isdeenergized by the disengaging of from contact cym! and the C phase gosignal CGS is energized by the engagement of armature cyxl with contact01013 and the engagement of armature cgl with contact 092.

The-separation of armature col from contact col extinguishes the phase Cstop signal CBS and deenerg izes relay DG. The deenergization of relayDG extinguishes the phase D warning signal DYS by opening its circuit atcontact 11572 and energizes the phase D stop signal DRS by theengagement of armature dgI with contact The cam shaft now rests inposition 5 with the go s gnal displayed to phase C and the stop signaldisplayed in phases A, B and D.

We have now considered in detail thetransfer of the right of way fromphase A to phase B or phase C. The transfer of the right of way fromphase B to phase C or phase A is accomplished in a similar manner whichwe will now consider in somewhat less detail.

When the right of way is leaving phase B and is next to be accorded tophase C, the cam shaft moves from position 3 to position 4 whereupon Irelays BYQK, CYX andDY are energized in ac- G signal sequence.

signals to be energized in phases B and D but occasions no signaldisplay change in phase C wherein the stop signal remains displayed inaccordance with the requirements of the G, A,-R, R, The circuits for allof these signals have been previously traced.

At the end of the phase B warning signal period the cam shaft moves intoposition 5 the phase C go signal position, wherein it remains during thephase C go signal period. Relays BYX, CYX, BG, DG and DY are thereforedeenergized and relay CG is energized. The circuits of all of theserelays have been previously traced.

The energization or deenergization of the relays as mentioned abovecauses the warning signals to be extinguished, andthe stop signal to bedisplayed, in phases B and Diand causes the go signal to be displayed inphaseC.\.. 'Ihe circuit changes by which these signal changesjareeffected have been previously. described.

-We have. considered above the functionin of the signal control circuitsto transfer the right of way is to be transferred from phase B to phaseA, omitting the phase C go signal display, the

apparatus operates as follows:

As the cam shaft moves into position 4 relays BYX, AYX are energized andthey, with relay BG, are held continuously energized while the cam shaftis stepped rapidly around to position 6 wherein it remains with theabove mentioned relays continuously energized for the normal phase Bwarning signal period as has been explained. During this period thephase Bgo signal is extinguished and the phase B warning signal isenergized by the operation of relay BYX. The operation of relay AYX isof no effect as has been previously explained. The phase D signaldisplay is not affected since neither relay DG or DY is changed.

At the end'of the normal phase B warning signal period the cam shaft ismoved into position 1, the phase A go signal position, whereupon relaysAYX, BYX and BG are deenergized and relay AG' is energized, as has beenexplained. This causes the phase B warning signal and the phase A stopsignal to be extinguished and alsocauses the phase A go signal and thephase B stop signal to be energized in accordance with the previous lyexplained operation of their circuits.

When the right of way is to be transferred from phase C to phase A, themovement of the cam shaft into position 6 causes the operation of relaysCYX DY and AYX which causes the phase C go signal to be extinguishedand. the phase C warning signal to be energized in accordance I with thepreviously explained operation of their circuits. No other signalchanges occur in this cam shaft position.

At the end of the phase C warning signal period the cam shaftmoves intopositioni, the phase A go signal position, whereupon relays CYX, DY,

AYX and CG are deenei'gized and relays AG and DG are energized whichcauses the phase C waming signal, the phase D stop signal and the phaseA stop signal to be deenergized and in addition causes the phase A andphase D go signals to

